Conventionally, yttria-stabilized zirconia is widely used as a ceramic electrolyte of a solid state fuel cell. However, the conventional solid state fuel cell is operated at a very high temperature about 1000° C. to ensure yttria-stabilized zirconia to exhibit high ionic conductivity. To reduce the operating temperature of a solid state fuel cell, many approaches are being investigated, for example, (1) Adrien Vincent et al., “Elaboration and ionic conduction of apatite-type lanthanum silicates doped with Ba, La10−xBax(SiO4)6O3−x/2 with x=0.25-2,” Journal of the European Ceramic Society 27 (2007) 1187-1192, (2) A. Inoubli et al., “Influence of anionic vacancies on the conductivity of La9.33Si6−xAlxO26−x/2 oxide conductors with an oxyapatite structure,” Journal of Power Sources 271 (2014) 203-212, and (3) Jun Xiang et al., “Synthesis and electrical conductivity of La10Si5.5B0.5O27+δ (B=In, Si, Sn, Nb) ceramics,” Solid State Ionics 220 (2012) 7-11.
There is no prior art or literature which discloses a solid state fuel cell including a ceramic electrolyte having a silicate oxyapatite doped with alkali metal cations.